Air purification system

Abstract

An air purification system that comprises a substrate, and at least one layer of photocatalysts. The at least one layer of photocatalysts further comprise a plurality of metal clusters.

The invention claimed is: 
     
       1. An air purification system, comprising:
 a substrate; and 
 at least one layer of photocatalysts, comprising a plurality of metal clusters; 
 wherein the plurality of metal clusters are present in a lower concentration in a first region of the at least one layer of photocatalysts than in a second region of the at least one layer of photocatalysts, wherein said first region is exposed to ambient air. 
 
     
     
       2. The air purification system of  claim 1 , wherein the substrate is an aluminum honeycomb. 
     
     
       3. The air purification system of  claim 2 , wherein the photocatalyst is titanium dioxide, doped titanium dioxide, metal oxide grafted titanium dioxide, zinc oxide, tin oxide, or any mixture thereof, and wherein the doped titanium dioxide has a dopant that increases the photocatalyst's activity. 
     
     
       4. The air purification system of  claim 3 , wherein the photocatalyst comprises doped titanium dioxide, wherein said doped titanium dioxide has a dopant that increases the photocatalytic activity of said doped titanium dioxide when compared to titanium dioxide. 
     
     
       5. The air purification system of  claim 1 , wherein the plurality of metal clusters comprises one or more noble metals. 
     
     
       6. The air purification system of  claim 1 , wherein the plurality of metal clusters comprises gold or gold mixed metal, and wherein the at least one layer of photocatalysts comprises about 2% or less by atomic ratio of an anchoring agent. 
     
     
       7. The air purification system of  claim 6 , wherein the anchoring agent is iron. 
     
     
       8. The air purification system of  claim 1 , wherein the plurality of metal clusters are present in an amount of about 0.1% to about 0.3% by weight in said first region, and wherein the plurality of metal clusters are present in an amount of about 1.5% to about 2% in said second region. 
     
     
       9. The air purification system of  claim 1 , wherein the plurality of metal clusters have a width of about 2 nanometers or less, and have a depth of 3 or fewer atomic layers. 
     
     
       10. The air purification system of  claim 1 , wherein the at least one layer of photocatalyst is arranged in a porous structure, and are coated with a layer of fused silica. 
     
     
       11. The air purification system of  claim 1 , wherein the at least one layer of photocatalyst comprises photocatalyst crystals, the plurality of metal clusters being deposited on the photocatalyst crystals before the photocatalyst crystals are applied to the substrate.